Figure 1

(a) Schematic diagram of the crystal structure for Si and CuI. Si is the diamond-crystal type lattice characterized by four covalently bonded Si atoms. The zinc blende lattice of cuprous halides crystals such as CuCl, CuBr and CuI consists of two interpenetrating face-centered cubic (fcc) lattices displaced along the diagonal of the body. Cu atoms on one fcc lattice and halogen atoms on the other side form the isomorphic structure minimizing the electrical polarization. (b) X-ray diffraction (XRD) 2θ scan of the CuI thin film (sample #3) grown on a Si substrate. The XRD peaks of CuI correspond to the (111) and (222) planes. (c) Transmission electron microscopy (TEM) image of the single crystalline structure of CuI grown on Si substrate. High resolution images and corresponding FFTs in the inset are obtained from each section of Si substrate and CuI film.